Acquisition (Narrative) (Details) $ in Thousands	1 Months Ended		3 Months Ended			6 Months Ended
	Jun. 30, 2019 USD ($) MMBoe	Dec. 31, 2018 USD ($) MMBoe	Jun. 30, 2019 USD ($) MMBoe	Jun. 30, 2018 USD ($)	[1]	Jun. 30, 2019 USD ($) MMBoe	Jun. 30, 2018 USD ($)	[1]
Business Acquisition [Line Items]
Revenue from sales to customers			$ 646,114	$ 426,767		$ 1,236,664	$ 823,096
Income (loss) from continuing operations before income taxes			$ 107,939	$ (22,563)		$ 141,684	$ (43,621)
LLOG Exploration Offshore L.L.C. and LLOG Bluewater Holdings, L.L.C.
Business Acquisition [Line Items]
Proved reserves | MMBoe	67		67			67
Cash consideration paid to PAI	$ 1,226,261
Revenue from sales to customers			$ 43,600			$ 43,600
Income (loss) from continuing operations before income taxes			8,000			8,000
LLOG Exploration Offshore L.L.C. and LLOG Bluewater Holdings, L.L.C. | Sales Thresholds 2019 to 2022
Business Acquisition [Line Items]
Contingent consideration, maximum	200,000		200,000			200,000
LLOG Exploration Offshore L.L.C. and LLOG Bluewater Holdings, L.L.C. | First Oil from Development Projects
Business Acquisition [Line Items]
Contingent consideration, maximum	$ 50,000		50,000			50,000
Petrobas America Inc
Business Acquisition [Line Items]
Proved reserves | MMBoe		97
Cash consideration paid to PAI		$ 788,724
Percentage of interest in subsidiary transferred		20.00%
Revenue from sales to customers			388,900			622,900
Income (loss) from continuing operations before income taxes			$ 136,800			$ 284,500
Petrobas America Inc | Sales Thresholds 2019 to 2022
Business Acquisition [Line Items]
Contingent consideration, maximum		$ 150,000
MP Gulf Of Mexico LLC
Business Acquisition [Line Items]
Parent ownership interest		80.00%
Petrobas America Inc | MP Gulf Of Mexico LLC
Business Acquisition [Line Items]
Noncontrolling ownership interest		20.00%

[1] Reclassified to conform to current presentation (see Note A).